Friday, November 11, 2011

How many species of Santa Cruz Cypress are there?

Botanists have not agreed upon use of categories to classify hierarchical
variation pattern. As I see it,
trinomials are a type of botanical hedge-fund.
We name a taxon (‘we buy it’), then we purchase a derivative against its
being ‘lumped’ as a hedge by treating it as an infrataxon. Moreover, there are no regulatory mechanisms
governing the choice of category in the hierarchy. Sound familiarly like a financial meltdown? Some authors publish boatloads of new
combinations because it is their habit to use solely a single category of infrataxon. Literature pollution?

The utility of recognizing infrataxa is not well codified in modern
usage. Hamilton & Reichard (1)
document the fact that most taxonomists employ only a single hierarchical category
below the rank of species, and that two schools of thought are evident: those
whom use the category “subspecies” or those that use “variety”. but few
botanists use both. As Fosberg (2) notes
there is no specific prohibition against the practice, perhaps due to an
instinctive aversion to quadranomials. The
vast majority of authors fail to provide a rationale for their choice of
infraspecific category, or for their viewpoint upon the question of parsing
variation into a hierarchical topology.

Recently, the question arises in the case of the Santa Cruz Cypress.
and endangered tree: Silba (3) named 5 subspecies. Adams & Bartel (4), eventually after some
hemming, treat 2. One might choose to treat
the Silba infrataxa as varieties within subspecies; others would want to make
them formae (although the nature of forma seem to lack consensus in the
literature: mostly forma are taken to be sporadic, rare phenotypes that may not
have a genetic basis, that is, the condition may be developmental; or, their
genetic basis is viewed as a mutation, albinism in flower color is an example. There
is arboricultural utility in considering the Silba infrataxa as cultivars would
be o.k. as “C.V.” would eliminate confusion, but unfortunately horticultural
nomenclature in practice is in my experience inaccurate.

I could question the decision as to how to parse variation within H.
abramsiana by noting that for some individuals of ‘neolomondensis’ their
chemical profile was as distinct as is ssp. butanoensis, and ‘opleri’ was about
as removed in the ISSR ordination but it also differed in mean cone width,
length and number of scales. Faced with
practical necessity, the Adams and Bartel treatment is useful, but one could
also craft an alternative classification just as readily.

The pattern of relationships Adams & Bartel find are suggestive of genetic drift following upon segmentation of a variable, ancestral panmictic population: in some respects, one answer is there are either no subspecies of Santa Cruz cypress, but there are five groves.

I will also make reference to the choice between treating these plants in
Cupressus as has been traditionally done: Little (6) made out our cypresses to
be polyphylletic within Cupressus. By aversion to lumping them into Juniperus (6)
out Hesperocyparis was cleaved. There is
also evidence that all cupressus are a single clade (7) I like the latter approach because by their
very nature genera are small (8) and in this instance the
Hesperocyparis-Cupressus division is a deep one.